1. Field of the Invention
The present invention relates to solid-state image apparatuses, driving methods therefor, and camera systems, and more particularly, to a solid-state image apparatus having a plurality of horizontal transfer sections (horizontal transfer registers), a driving method therefor, and a camera system using the solid-state image apparatus as an image-pickup device.
2. Description of the Related Art
There have been known solid-state image apparatuses, such as charge-coupled-device (CCD) solid-state image apparatuses (hereinafter called CCD image apparatuses), in which an image section formed of pixels arranged two-dimensionally is divided, for example, into four areas, and each area is provided with a horizontal transfer register, in order to increase the number of pixels or to provide a higher electric-charge transfer speed (such apparatuses are disclosed, for example, in Japanese Unexamined Utility Model Publication No. Hei-1-175074 and Japanese Unexamined Patent Application Publication No. Hei-5-22667).
Specifically, as shown in FIG. 7, an image section 101 is divided, for example, into four areas 101A to 101D vertically and horizontally. Horizontal transfer registers 102A and 102B are provided above the image section 101 for the upper areas 101A and 101B, and horizontal transfer registers 102C and 102D are provided below the image section 101 for the lower areas 101C and 101D.
Signal electric charges in the upper areas 101A and 101B are vertically transferred to the upper direction to the horizontal transfer registers 102A and 102B, then, are horizontally transferred to the right and left directions by the horizontal transfer registers 102A and 102B, and are output through output sections 103A and 103B as output signals outA and outB. Signal electric charges in the lower areas 101C and 101D are vertically transferred to the lower direction to the horizontal transfer registers 102C and 102D, then, are horizontally transferred to the right and left directions by the horizontal transfer registers 102C and 102D, and are output through output sections 103C and 103D as output signals outC and outD.
In CCD image apparatuses for HDTV, two-channel horizontal transfer registers have already been implemented (they are disclosed, for example, in Japanese Unexamined Patent Application Publication No. Sho-62-92587 and Japanese Unexamined Patent Application Publication No. Sho-63-117577). Specifically, as shown in FIG. 8, two horizontal transfer registers 112A and 112B are disposed in parallel for an image section 111, signal electric charges are horizontally transferred in parallel in units of two lines by the horizontal transfer registers 112A and 112B, and the charges are output as output signals outA and outB through two output sections 113A and 113B.
In the former conventional technology, that is, in the CCD image apparatus in which the image section 101 is divided, for example, into four areas and each area is provided with a horizontal transfer register, however, since the horizontal transfer registers 102A and 102B are driven in directions opposite to each other, and the horizontal transfer registers 102C and 102D are driven in directions opposite to each other, it is necessary to have at least two-way horizontal transfer pulses in four-phase drive, for example. In two-phase drive, since the horizontal transfer registers 102A and 102B need to have mirror-image structures, and the horizontal transfer registers 102C and 102D also need to have mirror-image structures, discontinuities occur at their boundaries, causing vertical-line noise.
Because the output signals outA and outB are output in different directions and the output signals outC and outD are also output in different directions, it is necessary to apply re-arrangement processing to the output signals outB and outD in a subsequent signal processing system, and the system becomes complicated. In addition, the image section 101 cannot be divided into three or more areas horizontally.
In the latter conventional technology, that is, in the CCD image apparatus having the two-channel horizontal transfer registers 112A and 112B, since signal electric charges in the image section 111 need to be transferred to the horizontal transfer register 112B through the horizontal transfer register 112A, the transfer electrodes of the horizontal transfer register 112A also serve as those used for transferring signal electric charges from the image section 111 to the horizontal transfer register 112B. Therefore, the channel width of the horizontal transfer register 112A cannot be extended. As a result, the amount of electric charges handled by the horizontal transfer register 112A cannot be increased. To obtain a sufficient amount of electric charges to be handled, it is necessary to make the amplitude of driving pulses for the horizontal transfer registers larger.